Multi-Area Interconnected Integrated Energy System Planning Considering Cloud Energy Storage

ObjectivesIn order to promote the efficient utilization of energy storage and user-side resources and improve the level of clean energy consumption, a multi-area interconnected integrated energy system planning model considering cloud energy storage was proposed.MethodsOn the basis of establishing the energy router model of the regional integrated energy system, a virtual energy router model considering electricity/heat/gas cloud energy storage was proposed. Aiming at the problem that cloud energy storage and integrated energy system belong to different investment entities, considering the limitation of the investment return period of cloud energy storage, a dual-subject two-stage planning model was proposed. In the first stage, the grid, equipment capacity and cloud energy storage price were planned. In the second stage, the operation strategy of the integrated energy system was optimized. Aiming at the high complexity of multi-energy flow grid planning, a pre-screening algorithm based on minimum spanning tree was proposed.ResultsThe example analysis results of a three-park integrated energy system planning show that the proposed model is helpful to improve energy efficiency, reduce carbon emissions, and improve the economic benefits of interconnected integrated energy systems.ConclusionsThe research reveals the potential of collaborative planning between cloud energy storage and multi-area integrated energy systems, and provides reference for the in-depth application and commercial promotion of multi-type energy storage in the energy field

Analysis of the Accuracy of an FDR Sensor in Soil Moisture Measurement under Laboratory and Field Conditions

Soil water content (SWC, % vol) is a key factor affecting plant growth and development. SWC measurement is vital to rational use of water resources for irrigation, and the accuracy of sensors in SWC measurement is of significant importance to smart data-driven irrigation. Here, a laboratory experiment and a field lysimetric experiment were conducted to evaluate the accuracy of Insentek sensors under various soil conditions (1.1 to 1.5 bulk densities and sand to clay soil textures) and irrigation levels (30, 45, and 60 mm), in 2018 and 2019. A microweighing lysimeter and oven-drying method were used as standard methods to compare the Insentek method. The root mean square error (RMSE, % vol) and relative prediction deviation (RPD) between the Insentek and microlysimetric SWC values were 0.89–1.04% vol and 5.6–6.8, respectively, under laboratory condition. The RPD value is larger than the threshold value of 4.0, indicating the accuracy of the Insentek sensors is reliable under laboratory condition. Except for 60 mm irrigation treatment, the RMSE between Insentek and the oven-drying method under field condition was 1.44–1.93% vol, and the RPD value was 1.56–1.93, lower than the threshold value of 4.0. The tiny gap between the Insentek sensor and soil may accelerate water infiltration along the probe 0-3 d after irrigation while increase air filling 5–7 d after irrigation, causing greater RMSE and lower RPD values. The dissatisfied performance in field condition may also be associated with the obvious drawbacks of oven-drying method, such as disturbance in soil sampling. When using oven-drying method to analyze the accuracy of the Insentek sensors in field condition, the concerns should be well addressed.</jats:p

Role of Hydraulic Signal and ABA in Decrease of Leaf Stomatal and Mesophyll Conductance in Soil Drought-Stressed Tomato

Drought reduces leaf stomatal conductance (gs) and mesophyll conductance (gm). Both hydraulic signals and chemical signals (mainly abscisic acid, ABA) are involved in regulating gs. However, it remains unclear what role the endogenous ABA plays in gm under decreasing soil moisture. In this study, the responses of gs and gm to ABA were investigated under progressive soil drying conditions and their impacts on net photosynthesis (An) and intrinsic water use efficiency (WUEi) were also analyzed. Experimental tomato plants were cultivated in pots in an environment-controlled greenhouse. Reductions of gs and gm induced a 68–78% decline of An under drought conditions. While soil water potential (Ψsoil) was over −1.01 MPa, gs reduced as leaf water potential (Ψleaf) decreased, but ABA and gm kept unchanged, which indicating gs was more sensitive to drought than gm. During Ψsoil reduction from −1.01 to −1.44 MPa, Ψleaf still kept decreasing, and both gs and gm decreased concurrently following to the sustained increases of ABA content in shoot sap. The gm was positively correlated to gs during a drying process. Compared to gs or gm, WUEi was strongly correlated with gm/gs. WUEi improved within Ψsoil range between −0.83 and −1.15 MPa. In summary, gs showed a higher sensitivity to drought than gm. Under moderate and severe drought at Ψsoil ≤ −1.01 MPa, furthermore from hydraulic signals, ABA was also involved in this co-ordination reductions of gs and gm and thereby regulated An and WUEi.</jats:p

Determining Threshold Values for a Crop Water Stress Index-Based Center Pivot Irrigation with Optimum Grain Yield

The temperature-based crop water stress index (CWSI) can accurately reflect the extent of crop water deficit. As an ideal carrier of onboard thermometers to monitor canopy temperature (Tc), center pivot irrigation systems (CPIS) have been widely used in precision irrigation. However, the determination of reliable CWSI thresholds for initiating the CPIS is still a challenge for a winter wheat–summer maize cropping system in the North China Plain (NCP). To address this problem, field experiments were carried out to investigate the effects of CWSI thresholds on grain yield (GY) and water use efficiency (WUE) of winter wheat and summer maize in the NCP. The results show that positive linear functions were fitted to the relationships between CWSI and canopy minus air temperature (Tc − Ta) (r2 &gt; 0.695), and between crop evapotranspiration (ETc) and Tc (r2 &gt; 0.548) for both crops. To make analysis comparable, GY and WUE data were normalized to a range of 0.0 to 1.0, corresponding the range of CWSI. With the increase in CWSI, a positive linear relationship was observed for WUE (r2 = 0.873), while a significant inverse relationship was found for the GY (r2 = 0.915) of winter wheat. Quadratic functions were fitted for both the GY (r2 = 0.856) and WUE (r2 = 0.629) of summer maize. By solving the cross values of the two GY and WUE functions for each crop, CWSI thresholds were proposed as being 0.322 for winter wheat, and 0.299 for summer maize, corresponding to a Tc − Ta threshold value of 0.925 and 0.498 °C, respectively. We conclude that farmers can achieve the dual goals of high GY and high WUE using the optimal thresholds proposed for a winter wheat–summer maize cropping system in the NCP

Determining Threshold Values for a Crop Water Stress Index-Based Center Pivot Irrigation with Optimum Grain Yield

The temperature-based crop water stress index (CWSI) can accurately reflect the extent of crop water deficit. As an ideal carrier of onboard thermometers to monitor canopy temperature (Tc), center pivot irrigation systems (CPIS) have been widely used in precision irrigation. However, the determination of reliable CWSI thresholds for initiating the CPIS is still a challenge for a winter wheat–summer maize cropping system in the North China Plain (NCP). To address this problem, field experiments were carried out to investigate the effects of CWSI thresholds on grain yield (GY) and water use efficiency (WUE) of winter wheat and summer maize in the NCP. The results show that positive linear functions were fitted to the relationships between CWSI and canopy minus air temperature (Tc − Ta) (r2 &gt; 0.695), and between crop evapotranspiration (ETc) and Tc (r2 &gt; 0.548) for both crops. To make analysis comparable, GY and WUE data were normalized to a range of 0.0 to 1.0, corresponding the range of CWSI. With the increase in CWSI, a positive linear relationship was observed for WUE (r2 = 0.873), while a significant inverse relationship was found for the GY (r2 = 0.915) of winter wheat. Quadratic functions were fitted for both the GY (r2 = 0.856) and WUE (r2 = 0.629) of summer maize. By solving the cross values of the two GY and WUE functions for each crop, CWSI thresholds were proposed as being 0.322 for winter wheat, and 0.299 for summer maize, corresponding to a Tc − Ta threshold value of 0.925 and 0.498 °C, respectively. We conclude that farmers can achieve the dual goals of high GY and high WUE using the optimal thresholds proposed for a winter wheat–summer maize cropping system in the NCP.</jats:p

Impacts of Irrigation Time and Well Depths on Farmers’ Costs and Benefits in Maize Production

In the North China Plain, drought usually occurs during the interval between wheat harvest and maize sowing in normal and dry years. The first irrigation for maize plays a critical role in guaranteeing seed germination and grain yields. Using experimental data from Xinxiang in 2019 and survey data of 641 farmers from the North China Plain in 2020, this study adopts a cost-benefit analysis method to investigate the impacts of irrigation time and well depths on farmers’ costs and benefits in maize production. The results showed that farms with well depth &gt; 120 m accounted for 49% of total farms, especially in Hebei Province, and 38% wells had low water yield &lt; 2.7 m3 kW−1 h−1. Delaying the time of the first irrigation made maize yields decline by up to 307 kg ha−1 day−1. Well depths increased irrigation costs and total maize production cost in an exponential manner, causing farmers’ benefits to decrease exponentially with well depths. With well depth &gt; 180 m, the proportion of irrigation cost to total cost rose to 14%, whereas well depth &gt; 230 m directly caused the farmers’ profits negative. A critical well depth of 230 m was put forward as the upper limit for farmers adopting maize planting in the NCP. The concept of ‘rotational irrigation strategy’ and suggestions of adopting drip irrigation, sprinkler irrigation, or hose-reel sprinkler irrigation were recommended to advance 6–8 days for the first irrigation period, compared with traditional flood irrigation.</jats:p